Steering gear



Deg. 23, 1941. H. HAWKINS 2,267,524

STEERING GEAR Filed Aug. 12, 1959 2 Sheets-Sheet l i7 Snvmtor attorneys H. HAWKINS STEERING GEAR Dec. 23, 1941'.

Filed Aug. 12, 1939 2 Sheets-:Sheet 2 1.... Q H2 i Q x Patented Dec. 23, 1941 UNITED STATES PATENT OFFICE 2,267,524 STEERING GEAR.

Harry Hawkins, Saginaw, Micln, assignmto Gen eral Motors Corporation, Detroit, Mich., a corporation of Delaware Application August 12, 1939, Serial No. 289,753

' 2 Claims. -(Cl. 74-499) This invention relates to improvements in ball Figure 1 is a sectional elevational view of the bearing screw and nut gears, of the type in gear witha part of the steering wheel and shaft which the screw and nut are provided withcorconnections broken away. responding helical grooves forming a helical pas- Figure 2 is a view substantially on line 22 of sage containing balls which constitute the screw Figure 1 with parts broken away and in section. thread connection between the screw and nut, Figure 3 is an enlarged detailed view of a part and especially to such a screw and nut gear in of Figure 1. which a limited number of balls is recirculated Figure 4 is a view similar to Figure 1 but enthrough the helical passage by means of a translarged with parts broken away and in section. fer retu t b Figure 5 is a greatly enlarged cross-sectional While the balls roll on the relatively moving view of the helical passage formed by the helical surfaces of the screw and nut, they rub in opgrooves in the screw and nut portions, with a ball posite directions against each other as they move in position therein. through the helical passage, and against the sides The steering shaft I, to which is secured the of the transfer return tube as they are pushed steering wheel 2, has a part provided with a therethrough by succeeding balls, and the frichelical groove 3 forming a screw 4, which is tional resistance to circulation of the balls mounted between suitable opposed thrust bearthrough such a circuit increases rapidly as the lugs 6 and I, in a housing 9. The bearing 6 is number of balls is increased. mounted in a sleeve portion I 0 of the housing 9 In cases where the gear is heavily loaded, and while the bearing 1 is mounted in a bore H of particularly where there is a cocking load tendthe end cover l2 of the housing 9. The outer ing to tilt the nut on the screw, it is desirable to race l3 of the bearing 1 is slidable in the bore have a suificient number of balls to extend II and ts position axially 0f the bo is j through several turns of the helical passage for able to take up end play of the shaft l by means a distance axially of thescrew which is considerof an adjusting screw l5 in the end cove ably greater than the diameter thereof. When which bears on an abutment H for the race l3 this is done, the resistance to movement of the and is' provided with a lock nut l8.

balls through the helical passage and through a 0n the screw 4, is a nut 20 having an internal transfer return tube for recirculation, may be helical groove 2| corresponding to the helical sufiicient to defeat any advantage in their use. oove 3 on the scr w o f a helical p s- The object of the invention is to reduce, the sage 22 containing balls 24, which constitute the total resistance to the movement of a given numscrew thread connection between the shaft I and her of balls through the helical passage of a ball the nut as Shown most clearly in gs. 2 and 4. bearing screw and nut combination. The cross section of the grooves 3 and 2| form- The above and other objects of the invention g th helical passage 22 is shown gre y will be apparent as the description proceeds. a ged in Fig. 5 and is such that the area of According to the invention the balls in the contact between the balls and the grooves is relahelical passage are divided into a plurality of tively small. separate and distinct trains, each of which is re- There a w para e and distinct trains 21 circulated through its own transfer passage in an and 28 of balls 24, in Spaced Parts f the el al independent closed circuit. It has been found pas e 2, and in order to maintain balls in the that this considerably reduces the frictional rehelical passage at all times, these trains 21 and sistance to movement of the balls, and hence to 28 are recirculated into the helical pas 22 relative movement between the screw and nut, through tra Passages constituted y transfer and that what would otherwise be a structure tubes 30 and 3| respec ywith prohibitive friction is made completely satis- The transfer tubes 30 and 3| are U-shaped, factory and advantageous. with parallel end portions inserted into parallel The drawings show the application of the indrilled orifices 34, 35 and 31, 38 respectively, ex-

vention to a steering gear suitable for an autotending to the outside of the nut and leading mobile, in which the nut is moved axially of the tangentially into and Out 0 pa P s Of the screw by rotation thereof, and is provided with helical pas teeth so as to constitute a rack which transmits The ends of the transfer tubes extend tanturning movement to a steering gear rock shaft, gentially into the helical passage 22, and when through a gear sector thereon. a the individual balls of each train reach either In the drawings: open end of their respective transfer tubes, they are guided thereinto and are pushed therethrough by succeeding balls, in one direction-or the other, according to the direction and degree to which the shaft! is turned.

In the example illustrated, all the orifices 34,

35 and 31, 38 are parallel and extend to one side of the nut 20, on to which the transfer tubes 30 and'll are clamped by a clipv 40, secured to the nut by screws ll;

, The underside of the nut 20 is formed as a toothed rack 45, meshingwith a complementary gearsector '46 formed on a rock shaft 41, sup--' ported in needle bearings "and 50, in the hous- 1X18,-

It will be noted that the teeth of the sector 46 are not formed on the side'of a segment of a cylinder, but rather on the side of a, segment of a cones There results a structure in which backlash between the rack and sector maybe -taken up by axial movement of the rock shaft 41, to the left as shown in Fig. 2. The'arrange-' ment of the teeth on the rack and sector results in a slight thrust of the shaft 41 against a thrust .button 5|, which is positioned to take up back-- lash by an adjusting'screw 53, threaded in a cover of the-housing 9, and secured by a lock nut 55.

A conventional pitman arm 51 is secured to the end 'of the shaft 41 remote from the adjusting screw 53, to transmit movements of .the rock shaft to the dirigible wheels of an automobile, through any suitable steering linkage (not shown).

It -will be apparent'that the teeth of the sector 46 prevent any turning of the nut 20, which is thusrestricted to movement axially of the sha I with turning of the latter.

distinct trains in parallel, each of which is recirculated through its own transfer passage in an'independent closed circuit, effects a considerable reduction "in the frictional resistance to be overcome, 'as compared with a structure in which the same number of balls is recirculated through a single and necessarily longer transfer passage, and thereby makes possible a ball bearing screw and nut gear in which, when necessary, a larger number of balls may be used than would otherwise be practicable.

I claim:

l. A steering gear including a helically grooved shaft mounted for rotation in suitable bearings, a nut on said shaft, moved axially thereof by rotation of the shaft, said nut having a helical internal groove corresponding with the helical groove on said shaft to form a helical passage containing balls which constitute the connection between the shaft and nut, two pairs of orifices in the nut, extending between spaced points of the helical passage-and the outside of the nut, the orifices of said pairs leading respectively tangentially into and out of spaced parts of said helical passage, two transfer return tubes each interconnecting the orifices of a pair and extend- The division of the number 'of balLs in the helical passage 22, into a plurality of. separate and which the two pairs of orifices and the transfer return tubes are on one side of the nut, and the rack teeth are on the opposite side, of the nut. HARRY HAWKINS. 

